Costantino N, Zuber M, Court D
Laboratory of Chromosome Biology, National Cancer Institute-Frederick Cancer Research Facility, Maryland 21702-1201.
J Bacteriol. 1990 Aug;172(8):4610-5. doi: 10.1128/jb.172.8.4610-4615.1990.
Two mutations in the ninR region of bacteriophage lambda that bypass a requirement for antitermination have been studied. One mutation, byp, has been cloned and mapped by marker rescue to a 417-base-pair segment in the ninR region of the genome. Analysis of the byp mutation by using promoter detection vectors, DNA sequencing, and S1 nuclease analysis showed that the byp mutation created a new promoter that transcribed gene Q. The second mutation analyzed was the deletion nin3. Sequence analysis revealed that 2,485 base pairs of the ninR region were removed, beginning within the ren gene and ending in an open reading frame termed ninG. The tR2 and tR3 terminators, and probably others, were removed by the nin3 deletion, thereby allowing the phage to be N independent and to grow in hosts defective for Nus antitermination factors.
对噬菌体λ的ninR区域中绕过抗终止需求的两个突变进行了研究。一个突变体byp已通过标记拯救克隆并定位到基因组ninR区域的一个417碱基对的片段上。利用启动子检测载体、DNA测序和S1核酸酶分析对byp突变进行分析，结果表明byp突变产生了一个转录基因Q的新启动子。分析的第二个突变是缺失nin3。序列分析显示，ninR区域的2485个碱基对被去除，起始于ren基因内，终止于一个称为ninG的开放阅读框。tR2和tR3终止子以及可能的其他终止子被nin3缺失去除，从而使噬菌体不依赖N，并能在对Nus抗终止因子有缺陷的宿主中生长。
